What benefits do "hotter" coils bring you versus stock? Any win on HP?

 Jim

In general, a coil only puts out whatever voltage is required to fire a spark plug, regardless of how much spark it's capable of. That's fine with a well maintained ignition system. What the performance coils do is have a much greater reserve of spark energy capability for wider gapped plugs, ignition systems that are less than optimum, plugs wires that have higher resistance, etc.   The coil will still put out what energy is necessary to fire the spark, but with the extra capability can also do so at higher rpm's.

High performance coils can be designed with higher towers, bridges between the terminals...all for various reasons. They normally have more coil windings internally. Most are oil filled...some are epoxy filled and are for high stress, high vibration applications.

Standard coils and ignitions are inductive, not to be confused with capacitive discharge ignitions. CD ignitions operate differently where they fire the spark plugs several times each firing cycle, at least at lower rpm's.

Performance coils in and of themselves don't create increased horsepower, etc. As part of a well thought out ignition system, they can help increase performance by ensuring more complete combustion. This can be more of a "seat of the pants" increase in responsiveness than might show up on a dyno. Just sticking a hotter coil in a car may make no difference at all if not matched to the needs of the car and other components.

All true.  Just one more factor.  A stronger coil will not fire at increased voltages as already stated.  But with more energy available, it will fire for a longer duration at the same voltage.  This is why it may burn more of the fuel in eh cylinder.   Of course if voltage output increases, duration of the spark will be less.

If the duration of a stock coil is too little due to very high KV demand (measure of power in voltage required to start the spark) the spark may stop before it should, and not burn all the fuel.   A stronger coil will maintain enough duration to light the fuel.

But as already said, most of the time in a stock engine it won't help you.   It's may be more than you need.  This is typically true of a stock engine with a HEI ignition.  A point system will usually benefit from the stronger coil.   Once the engine is modified, it can be a much different story.

MSD works due to the fact it starts the spark, then stops it before the coil is discharged by closing the primary circuit to the coil, and starting to charge the coil again.  It's too brief to actually charge the coil, but it does maintain what it still has.   Then it fires it again, stops, and fires agains.  This happens several times, depending on engine speed.  In effect it greatly increases total spark duration.   This can help a modified engine a GREAT deal.  And sometimes on a stock engine it may not produce more power, but may very well clean  up emissions and sometimes increase fuel mileage.  If it's a capacitive discharge ignition system, the operation is controlled differently, but the effect at the spark plug is the same.

kstyer38511.4065162037

I also believe for a stock HEI to benifit from a "hotter coil" you also need a moduale with more built in "dwell time" to gain any real benifit.

Absolutely correct.